1. Field of the Invention
The present invention relates to an optical disk recording/reproducing device for recording a signal on a disk using a laser irradiated from an optical pickup, and for reproducing such a signal recorded on a disk using a laser.
2. Description of the Background Art
Disk players for executing readout of signals recorded on a disk using an optical pickup are widely used. Recently, optical disk recording/reproducing devices are commercially available, which are designed for performing, in addition to reproduction, recording of signals on a disk by a laser irradiated from an optical pickup unit.
In such an optical disk recording/reproducing device, a pit is created on a disk using a laser beam. When the laser output is inappropriate, the pit size becomes too large or too small. To prevent this problem, a disk used in an optical disk recording/reproducing device includes a trial writing region on the innermost track side. After recording a signal in the trial writing region, the signal is reproduced and detected, and the output of the laser for recording is set according to the detected signal. This technique is disclosed, for example, in Japanese Patent Laid-Open Publication No. Hei 6-76288.
Using a laser output set as described above, a signal is then recorded in a data signal recording region provided on the disk. The signal recording operation is executed by applying to a laser element a pulse signal having a waveform as indicated by a solid line in FIG. 3(d).
A signal is recorded on a disk by creating a pit in a signal track on the disk using a light beam output from a laser element, and the pit is formed in a prescribed size. The signal recording operation is executed while rotating the disk at a predetermined constant linear velocity. In some of the recently commercialized optical disk recording/reproducing devices, the linear velocity for the rotation during signal recording operation can be increased to several times the predetermined linear velocity.
The pulse signal applied to the laser element is configured to have as in the waveform shown in FIG. 3(d), a peak level VP for executing a recording operation, a bottom level VB for executing a reproduction operation, and a land level, namely, an erasing level VE, for erasing a signal recorded on the disk. Laser output is varied corresponding to each level of the pulse signal. It is therefore necessary to accurately set each level of the pulse signal.
The levels constituting the pulse signal are adjusted by sampling portions having the respective levels and then adjusting based on the sampled data. When the disk rotation speed is increased, the pulse width of the pulse signal applied to the laser element for signal recording becomes reduced. Accordingly, when sampling a monitor signal obtained from a monitor diode so as to execute adjustment of laser output, the sampling time becomes shortened, resulting in a problem that level adjustment cannot accurately be performed.
As a method for solving the above problem, it is possible to obtain accurate sample data from a portion having an erasing level VE, the level in which sampling operation can be performed using a longer time, and to set the peak level VP for recording and the bottom level VB for reproducing based on the obtained data. However, setting of the erasing level VE at an optimal value does not ensure optimal setting of the peak level VP and the bottom level VB. Moreover, it is impossible to determine whether the peak level VP and the bottom level. VB designated by using the erasing level VE as the reference are actually set at their optimal values, and this limitation is causing degradation of recording quality.
An object of the present invention is to provide an improved method overcoming the above problem for setting a laser output in an optical disk recording/reproducing device.
According to the present invention, there is provided an optical disk recording/reproducing device which records a signal on a disk using a laser irradiated from a laser element driven by a pulse signal, wherein an average level of a monitor signal obtained when a basic pulse signal is applied to the laser element is detected, the presently detected average level is compared to a predetermined reference average level of a monitor signal of a reference basic pulse signal, and waveform of the basic pulse signal is corrected by adjusting a peak level and/or a bottom level of the basic pulse signal such that the detected average level matches the reference average level.
According to another aspect of the present invention, in the above optical disk recording/reproducing device, an average level of the monitor signal of the reference basic pulse signal is obtained and stored prior to recording. When recording a basic pulse signal in a trial writing region of the optical disk, an average level of a monitor signal of the basic pulse signal is detected, and the detected average level is compared to the average level stored in advance to perform waveform correction of the basic pulse signal.
In a further aspect of the present invention, there is provided an optical disk recording/reproducing device which records a signal on a disk using a laser irradiated from a laser element driven by a pulse signal, comprising a detector for detecting an average level of a monitor signal obtained when a basic pulse signal is applied to the laser element, a storing unit for storing, in advance, an average level of a monitor signal of a reference basic pulse signal; and a controller for comparing the presently detected average level to a predetermined reference average level corresponding to the stored average level, and for correcting waveform of the basic pulse signal by adjusting a peak level and/or a bottom level of the basic pulse signal to be output such that the detected average level matches the reference average level.
In a still further aspect of the present invention, in the above optical disk recording/reproducing device, the storing unit further stores data concerning a relationship of a peak level and an erasing level with respect to the average level in the basic pulse signal, and data concerning a relationship of the erasing level and a bottom level with respect to the average level.
In another aspect of the present invention, in the above optical disk recording/reproducing device, an average level obtained from a monitor signal of the reference basic pulse signal is stored in advance in the storing unit. When recording the basic pulse signal in a trial writing region of the optical disk, the detector detects the average level of the monitor signal of the basic pulse signal, and the controller compares the detected average level to the average level stored in advance to perform waveform correction of the basic pulse signal.
By performing the above-described processing, the waveform, especially the peak level, of the pulse signal actually being applied to the laser element during recording can be controlled to an appropriate value without actually detecting the peak level of the pulse signal.
According to a further aspect of the above optical disk recording/reproducing device of the present invention, when recording a pulse signal in an actual recording region of the optical disk, an output level of the basic pulse signal after waveform correction is adjusted such that the erasing level of the basic pulse signal is maintained at a predetermined level.
According to the correction processing as described above which can be executed using a simple arrangement, a basic pulse signal having an appropriate waveform, especially an appropriate peak level, set in advance based on an average level can be output to the laser element during actual recording.